They both really just tell you if you have allergies. They might hint at your worst allergens, but there are a lot of false positives and negatives with both tests.

The skin tests are more susceptible to errors if you've taken any allergy medication, even days before. Whereas the blood test is not affected.

Both tests can provide false negatives or positives. However are used to test for suspected culprits that caused previous reaction.Allergy doctors use these tests, plus patients history to determine the allergen. The downside of blood tests are that they can take two weeks before you have test results and have to make another appointment to understand the results and the impact a positive result will have on your life. Blood tests are also more expensive and skin prick tests are much cheaper. Skin prick tests produce results within mins and often a allergy doctor can then discuss the results with you there and then. Skin prick tests have been used since the 1960s. We have always had skin prick tests, and after a negative results we talked about food challenges, pro/cons etc and booked it if we thought it was needed. After positive results to new suspected allergen found it useful to know culprit and add it to list for ever. Hope this is helpful.

Oh and my allergy is bad enough to where I have to carry epi-pens.